The winged motometer on Grandpa's Model T. The chrome star on Mom's Mercedes. For decades, hood ornaments identified the beginning of a car and the height of an automaker's branding.

But styles change, and with them, hood ornaments have become the exception rather than the rule.

To understand the hood ornament, we must travel back over a century when automakers like Ford moved their engines from beneath the body to in front of it, exposing the radiator.

"On the old Model T's and Model A's, the 'ornament' was actually a radiator thermometer, so the driver could tell at a glance if the engine was about to overheat," said Carol Leigh, photographer of classic hood ornaments. "As cars became sleeker, more elegant, the radiator thermometer morphed into a sign of luxury, a prominent advertisement of sorts for the car, and a symbol of more modern times."

Automakers entered a radiator-topped arms race that strengthened their brands. The Jaguar leaper, Pierce Arrow archer and Plymouth Mayflower bridged the Jazz Age into Art Deco bliss. Chrysler's winged logo first flew from a radiator. Bentleys wore B's on their bonnets. By the 1950s, cars embraced the Jet Age with bombsights and jet planes on hoods and fenders.

No ornament is more famous than the "Spirit of Ecstasy" that has topped Rolls-Royce grilles since 1922. Created by sculptor Charles Sykes, it originally was 7 inches tall, but is now 3 inches and can retract into the radiator shell for protection. The sculptures are created in 24-karat gold, sterling silver, glass, stainless steel and illuminated versions. In 2011, Mouawad Jewelers created a diamond-enrobed version valued at $250,000.

The hood ornament on a 1920 Ford Model T was actually a radiator thermometer.

The Cadillac crest still exists but has fallen from the hood to the grille. This downward regression has affected Mercedes-Benz, too.

"When Gottlieb Daimler built the first Mercedes cars around the turn of the 20th century, the cap of the coolers where customers filled in the water was the ideal platform for his brand logo," said Gorden Wagener, chief design officer at Mercedes-Benz. "The three-pointed star on the hood, especially on the S-Class, is the symbol of a traditional Mercedes three-box luxury limousine. Our specific grille design with the star on the hood represents sovereignty, desirable luxury and is famous around the world."

Leigh likely knows hood ornaments better than anybody. She has photographed countless versions for her website (carol-leigh.pixels.com/collections/old+cars+parts).

"I've been photographing hood ornaments since the mid-1980s and never tire of the quest to find different backgrounds and shadows for my photo files," Leigh said.

There's the ethereal "Silver Streak" ornament from a 1939 Pontiac that, she said, looks "Batman-esque and implies a sense of power" and the Griffin from a 1933 Essex Terraplane that's "fierce and substantial," though pitted with time. Other gems include the "space-age Airplane Jet Eagle" from the 1955 Chevrolet Bel Air and arching chrome quail from a 1931 Ford. Look through her collection to see the sleek greyhound from a 1936 Ford, graceful stretching lady from a 1933 Oldsmobile and Continental star shadowing an orange hood.

"They may seem passé today, but hood ornaments always catch my eye," Leigh said. "They fascinate me because they are different from one another, look cool, and often symbolize the history of America. I find them all beautiful, from the pitted metal Griffin to the sleek female figure sweeping backward, they all look great to me."